More than 5 million years ago, the evolutionary path of humans split from that of other primates. And now – after a mere 25 years of intensive research – scientists in Dresden, Germany have identified the gene responsible for creating this divergence and leading the human brain to become the most complex structure in the known Universe.

The gene, which is known as ARHGAP11B, is a modified version of a common DNA strand that is found in yeast as well as mice. The modification is evidently responsible for the proliferation of neurons in the neocortex.

Wieland Huttner, director of the Max Planck Institute of Molecular Cell Biology and Genetics in Dresden, led the research and told reporters, “Our ultimate goal has always been to identify the changes in the genome that were responsible for us humans having larger brains than other primates.”

The human brain has almost tripled in size in the last 7 million years. Its 100 billion neurons, which consume 20% of our energy, have more connections than there are stars in the Milky Way.

Of course, size isn’t everything. And some scientists are exploring specializations at the cellular level

Researchers injected the gene into the brain of mouse embryos to see if they, too, would grow bigger brains. Indeed they did – with 50% of them growing the crinkled brain surface that allows more brain tissue to fit into the skull. Why this happens only half the time, and whether it will result in increased learning capacities in the mice, is as yet unknown.

Marta Florio, a neuroscientist at the Dresden lab and the first author listed in a report on the research published in the journal Science, has discovered 56 genes that affect stem cells in the brains of primates. About a quarter of these genes are unique to humans and some had never before been identified. Their impact on human brain development is as yet unknown.

As for whether an injection of ARHGAP11B into rat embryos will result in creating super-intelligent rodents, Florio is skeptical. She says, “You’d predict the mice would have more computational power, but the neurons have to form a network, and I’m skeptical that with one gene you will get that. It’s an exciting possibility, but we should be cautious about that happening.”

What has been demonstrated already is that mice whose brains have human brain cells grafted onto them actually do outperform unaltered mice in their ability to learn and to remember.

News summary by Laurel Airica.  Check out Laurel’s YouTube channel to see what her brain has cooked up.

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